Avoid wraparound when casting unsigned size_t to signed ssize_t.
Practically, this only affects a perl compiled with 64-bit IVs on a 32-bit
system. In that instance a value of count >= 2**31 would turn negative
when cast to (ssize_t).
(cherry picked from commit 94e529cc4d56863d7272c254a29eda2b002a4335)

Prevent premature hsplit() calls, and only trigger REHASH after hsplit()
Triggering a hsplit due to long chain length allows an attacker
to create a carefully chosen set of keys which can cause the hash
to use 2 * (2**32) * sizeof(void *) bytes ram. AKA a DOS via memory
exhaustion. Doing so also takes non trivial time.
Eliminating this check, and only inspecting chain length after a
normal hsplit() (triggered when keys>buckets) prevents the attack
entirely, and makes such attacks relatively benign.
(cherry picked from commit f1220d61455253b170e81427c9d0357831ca0fac)

fix NAME of perl5125delta.pod2012-11-10T17:43:53ZDavid Mitchelldavem@iabyn.comDominic Hargreavesdom@earth.li2012-11-10T17:43:53Zhttps://perl5.git.perl.org/perl.git/commitdiff/f06ec69fb39d3ee46fd11b641064c49fb8dc717c

bump version to RC22012-11-07T21:12:45ZDominic Hargreavesdom@earth.liDominic Hargreavesdom@earth.li2012-11-07T21:12:45Zhttps://perl5.git.perl.org/perl.git/commitdiff/cf754a72fba75f09ea583456399e3e9f58beccdf

bump version to RC12012-11-03T13:19:11ZDominic Hargreavesdom@earth.liDominic Hargreavesdom@earth.li2012-11-03T13:19:11Zhttps://perl5.git.perl.org/perl.git/commitdiff/84462eea9ace747aa9becb0485fb879bdc8813bf